The development of haze in fruit beverages, particularly apple juice, has long been a distinct problem, since both product aesthetics and taste are affected by it. Fruit juices are turbid by nature, and the flocculation which develops after storage compounds the degree of haziness encountered in such products. It is believed that proteins in association with polyphenols are primarily responsible for the haze formation in fruit juices and the prior art abounds with processes designed to result in haze removal and stabilization upon storage of fruit juices.
To a significant extent, the haze problem in fruit beverages has been treated through the use of enzymes which hydrolyze proteins which normally form haze with the phenolic components of the fruit preparation. Such beverages include, for example, apple, cranberry, grape, citrus fruit, peach, pear, plum, apricot and nectarine juices. Prior art documenting the use of these protein decomposing enzymes can be found in the form of U.S. Pat. Nos. 995,826; 3,055,757; 3,597,219 and 3,597,220. However, such enzymatic treatment of beverages is not advantageous. The decomposition and removal of protein also reduce the nutritive value and have a deleterious effect on the flavor of beverages. Further, the remaining enzymes might adversely affect the quality of the beverages. For example, a decomposition product of the enzyme tends to be associated with polyphenols and causes haze or turbidity when fruit juices are stored for prolonged periods.
Another approach to the haze problem in fruit beverages has been and continues to be the the use of adsorbents. Adsorbents which has been proposed in the prior art include polyvinyl pyrrolidone as taught in U.S. Pat. No. 2,698,550 and water-insoluble polymers of vinylpyrrolidone, i.e., polyvinyl polypyrrolidone according to U.S. Pat. Nos. 2,875,062; 2,939,791 and 2,947,633. In U.S. Pat. No. 3,940,498, haze control agents comprising polyamides such as NYLON 66 blended with synthetic magnesium silicates are described, and these may be used in conjunction with other haze control agents such as hectorite and acid-activated bentonites as well as with the protein modifying enzymes, all of which are taught in U.S. Pat. No. 3,251,693. Furthermore, the haze control agents taught in U.S. Pat. No. 3,940,498 may also be used as components of a blend with other components, including filter aids such as perlite or diatomite.
One particularly useful adsorbent used in various forms as a haze control agent in fruit beverages as well as alcoholic beverages has been silica. Various patents teach the use of silica in a sol form as an effective haze control agent, by itself or in conjunction with other agents. Silica aquasols, generally known as silica sols, are colloidal solutions of silicon dioxide in water. In U.S. Pat. No. 4,027,046, teachings are found which indicate the effectiveness of fining protein-containing beverages with an aluminate-modified silica sol. In addition, U.S. Pat. No. 4,109,017 describes clarifying fruit juice with pectinase, with subsequent settling taking place in the presence of silica sol. In U.S. Pat. No. 4,211,799, a juice clarified with pectinase is stabilized against subsequent turbidification by post treatment of the juice with silica sol.
Other prior art teaches the use of silica in a gel form as an effective haze control agent for alcoholic beverages such as beer. Silica gel, an amorphous silica colloid in which the dispersed phase has combined with the continuous phase to produce a viscous, jelly-like product, is ordinarily prepared by the acidification of sodium silicate. In U.S. Pat. No. 2,316,241, beer is treated with an "alkalized silica gel," i.e., a silica gel which is treated with alkaline liquids before said silica gel has had an opportunity to shrink upon drying. Further, in U.S. Pat. No. 3,617,301, a process to prevent haze formation in beer is taught, said process comprising treatment with a silica hydrogel of high surface area. U.S. Pat. No. 3,436,225 teaches silica gel used in conjunction with alcoholic beverage clarification; it combines aluminum silicates with silica gel, claiming to be able to reduce the silica gel requirement.
Prior art documentation of the silica gel application in beverage clarification is generally limited to use in beer clarification, and is characterized by the need to combine the silica adsorbent with some other component, either by simultaneous treatment using the silica-containing blend or with a separate silica treatment step.
It is therefore an object of the present invention to provide a clarification agent which will not require blending with any other agents to effectively remove turbidity in fruit beverages, particularly apple juice.
It is a further object of the present invention to provide a single component clarification agent which will effectively remove haze in apple juice without affecting its properties, namely pH and color. These and other objects will become apparent as the description of the invention proceeds.